The Effects of Essential Oils and Organic Acids on Microbiological and Physicochemical Properties of Whole Shrimps at Refrigerated Storage

The objectives of this study were to determine the effects of Essential Oils (EOs) and Organic Acids (OAs) on microbiological and physicochemical qualities of whole shrimps stored at 4 degrees C. Shrimps of 1.1 kg were dipped in solutions of EOs (cinnamon oil, garlic oil and lime oil) and OAs (lactic acid, tartaric acid and sodium diacetate) at 1:2 shrimp/treatment solution (w/w) at 25 degrees C for 30min. Concentration of sodium metabisulfite and distilled water (DH2O) were used as positive and negative controls, respectively. Shrimps were drip-dried for 5 minutes, packaged and stored in a chiller (4 degrees C) for 10 days. They were analyzed for microbiological (total aerobic plate count) and physicochemical (pH, colour and texture) properties at days 0, 2, 5, 7 and 10. Total aerobic plate count (TPC) of shrimps decreased immediately after dipping in solutions containing EOs, OAs and their mixture ratios. However, the TPC of shrimps continued to increase during storage and at day 10, TPC was significantly (P<0.05) higher compared to other days. Mixtures of tartaric acid and cinnamon oil was the best in controlling TPC in shrimps. pH of shrimps ranged from 6.60 to 7.86. Most of the treatments had significantly lower pH compared to DH2O treated shrimp. L* values (Lightness), a* values (Redness) and b* values (Yellowness) ranged from 32.57-42.27, -1.90-4.39 and 3.14-10.67, respectively. The texture (hardness value) of the shrimps ranged from 1135.4-2511.8 and decreased throughout storage period except solutions of lactic acid and lime. Storage of shrimps in EOs and organic acids can serve as an alternative for the preservation of shrimps other than low temperature storage.